1. Field of the Invention
The present invention relates to an image forming apparatus. More particularly, it relates to a technology of performing image forming in accordance with a sheet size of an image transfer sheet.
2. Description of the Related Art
Conventionally, there has been a known image forming apparatus in which a document size and an image transfer sheet size are detected, and an image transfer sheet having a sheet size matching with the document size is selected, and then image forming is performed, with use of a copying function or the like. Further, another image forming apparatus is known which has a function of performing image forming to an image transfer sheet (for example, an image transfer sheet set on a manual feeding tray) without enlarging or reducing a document size even if image forming is performed to an image transfer sheet having a sheet size different from that of the document (for example, Japanese Patent Unexamined Publication No. H06-148990).
However, according to the image forming apparatus so configured as described above, for example, in the case where image forming is performed with respect to an image transfer sheet having a sheet size which is smaller than a document size, and a document image exists at a portion beyond the image transfer sheet, toners remain on a photoconductive member and are not transferred to the image transfer sheet, so that it causes problems such as waste of toners and damages to the photoconductive member and peripheral equipments.
Further, when a designated sheet size of an image transfer sheet is different from a sheet size of an image transfer sheet actually set on a manual feeding tray (an image transfer sheet on which an image is actually formed), a post processing apparatus (finisher) is so set as to perform an operation suitable for the designated image transfer sheet size. Accordingly, since the sheet size of the image transfer sheet actually conveyed is different, for example, problems occurs, such as (1) a jam caused by abnormality in a width adjustment of an image transfer sheet which is subjected to post-processing, and (2) a jam error detected when an image transfer sheet having a sheet size larger than a sheet size so set as to be subjected to the post-processing is conveyed to the post processing apparatus, a sheet-feeding sensor provided in the post-processing apparatus detects an unexpected sheet size which is larger than the set sheet size since a driver used for the image forming processing with respect to the image transfer sheet is suitable for the set sheet size.